Office buildings and various types of commercial buildings are typically heated and cooled using rooftop, floor by floor, or central station air handling units. Supply ducts are installed in the interstitial space that is located above the ceiling and below the structural roof. The supply ductwork extends from the air handling unit to a number of air diffusers that are often mounted on the ceiling. Suspended tile ceilings are common in this type of building, and the diffusers are usually integrated into the ceiling tile system, along with lights, sprinklers, smoke detectors, electrical outlets and sometimes other devices such as cameras, motion detectors, speakers and various other fixtures. The return air system may include a number of return air grills that are built into the ceiling tiles and connected with return air ductwork that directs return air back to the air handling unit.
Although systems of this type have long been in widespread use, they are not wholly free of problems. The need to install extensive ductwork above the ceiling creates a large cost factor and adds significantly to the labor costs that are involved in constructing and finishing the space. The ductwork also occupies a large amount of space and reduces the space that is available for other components and equipment that must be installed in the interstitial space. The delivery of conditioned air is often less than ideal from an efficiency and comfort standpoint. In the latter respect, the air return system can be significantly mismatched relative to the supply system so that the rooms in the space can be uncomfortably warm at times and uncomfortably cool at other times. The need to provide separate fixtures for the supply and return systems also increases the cost of fabrication, shipping, handling, storage and installation of the fixtures. The need for two different fixtures for the supply and return systems also adds to the clutter on the ceiling and detracts from the ceiling aesthetics.
Other problems with conventional air delivery systems can arise from undue humidity in the supply ducts. This can lead to fouling of the ductwork with mildew, mold, fungi, and various micro-organisms that can create unhealthy conditions in the occupied space.
Although a variety of styles, from large rectangular units to rounded knobs, are available currently, most thermostats are visually unappealing. Conventional thermostats are normally simple rectangular boxes or dome structures that are mounted to protrude from the wall and are designed as stand alone products. In fact, it appears that thermostat manufacturers have not placed any great emphasis on whether their devices could match the decoration of the room where the device was located. In fact, the exterior color and design of current devices appear arbitrary and directed to the device as a stand-alone product.
Even though attempts have been made to enhance the aesthetics of thermostats in recent years, their appearance has not been integrated effectively into the overall decor of the room. The color and design of the thermostat have not matched other common wall mounted devices such as light switches, electrical receptacles, telephone and cable television outlets, communications devices such as intercoms, and other wall fixtures such as occupancy sensors and the like. As a result, thermostats often detract appreciably from the aesthetic appeal of the rooms in which they are installed.
Recently, state and federal laws have addressed the mounting height and accessibility of thermostats. These requirements make the aesthetic functions and appearance of thermostats more important because mounting height requirements often place the thermostat directly adjacent to the light switch and other similar electrical devices. Currently, most thermostats are intended for surface mounting, either directly or using a sub-base that contains wiring termination points. While some thermostats include adaptors that allow the thermostats to be mounted on a standard electrical junction box, these configurations do not produce an integrated appearance with the other devices. It would be an aesthetic improvement if the thermostat could match these electrical devices in terms of size, color, shape and mounting method.
Thermostats have also suffered from relatively large dead bands that can result in the actual room temperature fluctuating 5° or more from the temperature setting. The need for anticipation circuits has added to the cost and complexity of the thermostat, as well as to problems with reliability.
In accordance with prevailing industry practices, many buildings are separated into several different air delivery zones that are each equipped with an individual air handling unit and separate ductwork. For example, a building may be divided into four separate quadrants that each has a peak requirement for a 25 ton air handling unit. In such a case, four 25 ton units are installed, each dedicated to its own zone and each connected with its own separate system of supply and return ducts. Each of the zones is subjected to its peak loading at a different time of day because of the movement of the sun and change of the sun angle throughout the day. Consequently, the overall simultaneous peak loading for the building as a whole may be 80 tons. Nevertheless, each air handling unit must be large enough to handle the maximum capacity for its own zone, so four 25 ton units are required even though 80 tons is the peak overall building load. The 20 tons of excess capacity adds markedly to the equipment expense, the installation and maintenance costs, and the energy that is used. The need for unduly large air handling units also detracts from the aesthetics of the building and increases the roof profile due to the need to install relatively large air handling units there.